The Proteus is a new product providing users with a robust, repeatable, low maintenance sensor platform for measuring BOD in real-time. The Proteus is underpinned by comprehensive research exploring the use of in-situ fluorescence as a technique for real-time BOD measurement. The Proteus is a multi-parameter instrument and for standard BOD configuration – a tryptophan-like fluorescence (TLF) sensor, turbidity sensor (see Fig. 2) and thermistor – provide users with real time measurement of reactive dissolved organic matter found in sewage and slurry, negating the need for a 5-day BOD laboratory analysis. Using a robust correction algorithm the tryptophan signal is corrected, in real time, for known interferrants. The result is a repeatable and highly accurate measurement that can provide instantaneous BOD measurement with a simple site specific calibration.